This invention relates to a mine roof support unit, and to a longwall mineral mining installation.
A longwall mineral mining installation usually has a conveyor (such as a scraper-chain conveyor) extending alongside the longwall face. The conveyor supports a guide, along which a winning machine (such as a plough) is reciprocably driven to win mineral material from the face. A plurality of roof support units are positioned side-by-side on the goaf side of the conveyor. The roof support units are provided with advance mechanisms, which are connected to the conveyor. The advance mechanisms are used to advance the conveyor, and then to advance the roof support units themselves in a follow-up movement.
In one known arrangement, each roof support unit has its own advance mechanism, which has a pair of guide rods and a hydraulic advance mechanism. The front (face-side) ends of the guide rods of each advance mechanism are connected to the conveyor by means of a common head-piece. The rear (goaf-side) ends of these guide rods are attached to a slide piece slidably guided on the floor sill of the associated roof support unit. The advance ram of each advance mechanism is pivotably attached to the associated floor sill and to the associated slide piece. (see DE-OS No. 2 540 091).
It is also known to position the advance mechanisms between the roof support units, each advance mechanism being connected to the floor sills of both adjacent roof support units. In this case, each advance mechanism has a pair of hydraulic advance rams and a pair of guide rods; one ram, and one guide rod being associated with each of the adjacent floor sills. This arrangement is particularly useful in inclined longwall workings. (see DE-OS No. 2 758 663).
Problems arise, however, in longwall workings which are inclined and which do not extend at right-angles to their access galleries. In such a working, as the face is advanced, the roof support units move towards the lower gallery. Thus, from time to time, it is necessary to dismantle the lowest roof support unit (before it moves into the lower gallery); and to move that unit to the other end of the face, where it must be reconstructed and positioned in the working at the top end thereof. Because of the size and weight of known roof support units, and the constricted space within mine workings, these dismantling, transport and reconstruction operations are extremely troublesome and time-consuming. Moreover, when the roof support units used have a large transverse dimension, a large roof area at the end of the working is left unsupported when a roof support unit is dismantled.
The aim of the invention is to reduce the problems associated with the known installations.